Decade of Extreme Weather Bears Fingerprint of Climate Change

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Droughts, heat waves, flooding — humanity has faced the effects
of extreme, disastrous weather throughout history. But this past
decade set itself apart — thanks, at least in part, to
human-caused climate change, according to scientists.

Last year, the United States saw 14 weather-related events that
cost at least $1 billion apiece ; in 2003, Europe sweltered
through its hottest summer in at least 500 years; in 2010, record
rainfall brought the worst flooding in Pakistan's history; and
the list from recent years goes on.

These events occurred during a decade ranked as likely the
warmest for at least the past 1,000 years, according to Dim
Coumou and Stefan Rahmstorf, of the Potsdam Institute for Climate
Impact Research in Germany.

Is there a connection between the warming world and extreme
weather? Most likely yes, say Coumou and Rahmstorf.

"It is very likely that several of the unprecedented extremes of
the past decade would not have occurred without anthropocentric
global warming," they write in a study published Sunday (March
25) in the journal Nature Climate Change. [ Quiz:
Test Your Weather Smarts ]

Connecting weather with climate change is tricky — climate
scientists routinely say they cannot attribute a particular event
to human-caused climate change.
However, over time, global warming is expected to result in a
shift in the odds of extreme events.

Coumou and Rahmstorf, like other climate scientists, use the
metaphor of a loaded die: The results of one roll may or may not
be the result of the manipulated die. But after many rolls, the
skewed results become evident.

To find the fingerprints of climate change, they reviewed extreme
weather events going back to 2000 as well as research into
possible connections with global warming. The latter includes
computer modeling studies, such as one from 2004 that found the
risk of a heat wave of the magnitude of Europe's
2003 scorcher has likely quadrupled as a result of humanity's
effects on climate.

The duo say they found the fingerprint of climate change on
unprecedented heat waves and extreme rainfall over the past
decade. As for big storms — tropical cyclones and hurricanes,
including Hurricane Katrina in 2005 — the evidence is mixed, they
find.

The
link between extreme weather and climate change isn't new. A
recent report by the Intergovernmental Panel on Climate Change
identified an increase in hot days, heat waves and heavy
precipitation and predicted more to come as a result of global
warming.